Research on the infiltrations in an earth dam. Case study: Cuibul Vulturilor Reservoir, Vaslui County, Romania

The dam of the reservoir Cuibul Vulturilor, located on the Tutova river is an inhomogeneous earth dam with a maximum height of 15.0 m, with a clayey central core and lateral prisms made of clayey-dusty sands. For tracking the evolution of body dam seepage, 12 piezometers and a drainage pipe with discharge in the downstream connection channel of the bottom outlet are used. The paper presents the characteristic elements of the theoretical infiltration curve in the dam It also shows the hydro isohypses for the dam drawn with SURFER program, using the maximum hydrostatic levels in the piezometers measured in the year 2019. The distribution of the hydro isohypses across the dam is strongly influenced by the location of the piezometers and the other point of measuring the hydraulic head. The pattern circulation of the infiltration water inside the dam body could be studied with increased accuracy, if the dam had been equipped with several piezometers. Even in these conditions, it is clearly observed that the regime of infiltrations through the dam body is similar to the theoretical way of behavior.

Hydrodynamic Performance and Cavitation Analysis in Bottom Outlets of Dam Using CFD Modelling

Bottom outlets are significant structures of dams, which are responsible for controlling the flow rate, operation, or removal of reservoir sedimentation. The service gate controls the outlet flow rate, and whenever this gate is out of order, the emergency gate which is located at upstream is utilized. The cavitation phenomenon is one of the common bottom outlets’ problems due to the rapid flow transfer. The present research is a numerical study of the flow pattern in a dam’s bottom outlet for different gate openings by the use of Flow-3D software and RNG k-ε turbulence model. The investigation is carried out on the Sardab Dam, an earth dam in Isfahan (Iran). The maximum velocity for 100% opening of the gate and Howell Bunger valve is about 18 m/s in the section below the gate, and the maximum velocity for 40% opening of the gate is equal to 23.1 m/s. For 50% opening of the service and emergency gate in the valve’s upstream areas, the desired pressure values are reduced. Moreover, in the areas between the two emergency and service gates, the pressure values are reduced. The possibility of cavitation in this area can be reduced by installing aerators. The flow pattern in Sardab Dam’s bottom outlet has relatively stable and proper conditions, and there are no troublesome hydraulic phenomena such as local vortices, undesirable variations in pressure, and velocity in the tunnel, and there is no flow separation in the critical area of flow entering into the branch.

Hybrid Artificial Intelligence Methods for Predicting Air Demand in Dam Bottom Outlet

In large infrastructures such as dams, which have a relatively high economic value, ensuring the proper operation of the associated hydraulic facilities in different operating conditions is of utmost importance. To ensure the correct and successful operation of the dam's hydraulic equipment and prevent possible damages, including gates and downstream tunnel, to build laboratory models and perform some tests are essential (the advancement of the smart sensors based on artificial intelligence is essential). One of the causes of damage to dam bottom outlets is cavitation in downstream and between the gates, which can impact on dam facilities, and air aeration can be a solution to improve it. In the present study, six dams in different provinces in Iran has been chosen to evaluate the air entrainment in the downstream tunnel experimentally. Three artificial neural networks (ANN) based machine learning (ML) algorithms are used to model and predict the air aeration in the bottom outlet. The proposed models are trained with genetic algorithms (GA), particle swarm optimization (PSO), i.e., ANN-GA, ANN-PSO, and ANFIS-PSO. Two hydrodynamic variables, namely volume rate and opening percentage of the gate, are used as inputs into all bottom outlet models. The results showed that the most optimal model is ANFIS-PSO to predict the dependent value compared with ANN-GA and ANN-PSO. The importance of the volume rate and opening percentage of the dams' gate parameters is more effective for suitable air aeration.

Hybrid Artificial Intelligence Methods for Predicting Air Demand in Dam Bottom Outlet

In large infrastructures such as dams, which have a relatively high economic value, ensuring the proper operation of the associated hydraulic facilities in different operating conditions is of utmost importance. To ensure the correct and successful operation of the dam's hydraulic equipment and prevent possible damages, including gates and downstream tunnel, to build laboratory models and perform some tests are essential (the advancement of the smart sensors based on artificial intelligence is essential). One of the causes of damage to dam bottom outlets is cavitation in downstream and between the gates, which can impact on dam facilities, and air aeration can be a solution to improve it. In the present study, six dams in different provinces in Iran has been chosen to evaluate the air entrainment in the downstream tunnel experimentally. Three artificial neural networks (ANN) based machine learning (ML) algorithms are used to model and predict the air aeration in the bottom outlet. The proposed models are trained with genetic algorithms (GA), particle swarm optimization (PSO), i.e., ANN-GA, ANN-PSO, and ANFIS-PSO. Two hydrodynamic variables, namely volume rate and opening percentage of the gate, are used as inputs into all bottom outlet models. The results showed that the most optimal model is ANFIS-PSO to predict the dependent value compared with ANN-GA and ANN-PSO. The importance of the volume rate and opening percentage of the dams' gate parameters is more effective for suitable air aeration.

Guide for valuing mud extracted from dam reservoirs in Morocco

All over the world, dam managers are constantly confronted with the siltation of dam reservoirs. This natural phenomenon represents a menace to the safety of the dam; because sediments deposited amplifies the load applied to the dam and shut off the dam’s bottom outlet. It also reduces the usable capacity of the reservoir and degrades the quality of the water stored (pollution, eutrophication, turbidity, etc.). In arid and semi-arid countries like Morocco, de-silting stays the best solution for silted dams. However, when we de-silt dam reservoirs, we produce enormous volumes of mud, which represent potential pollution for the environment and occupy immense terrains. Our research was carried out on the possible uses of these sediments. It has enabled us to develop a valuation guide in Civil Engineering, Agriculture, crafts, and the environment sectors. This guide provides a framework for performing tests and analyses to do on the sediments to compare them with the limit values required by regulations and standards in several economic sectors. The results of these evaluations help us to find the most appropriate uses of the sediments in the sectors mentioned above.

Experimental study of pressure flushing of non-cohesive sediment through slotted pipe bottom outlet

ABSTRACT Among several techniques for prevention and mitigation of reservoir sedimentation, bottom outlets arise as a means of removing sediment deposited close to the dam. Given the reduced sediment removal provided by traditional bottom outlets under pressure flushing conditions, this article proposes a new type of structure that aims to increase sediment removal in the direction parallel to the dam axis. An experimental installation was employed to evaluate its operation as a function of the variation of its diameter and flow and sediment characteristics. Through analysis of the bathymetry generated by the structure, a dimensionless relation for predicting the scour pit length was obtained, presenting good fitness to the experimental data.

Assessment and Prediction of Air Entrainment and Geyser Formation in a Bottom Outlet: Field Observations and CFD Simulation

Air entrainment at the intake of a bottom outlet often gives rise to air pockets in its conduit and formation of geysers. The outlet in question comprises a bulkhead gate, gate shaft, horizontal conduit, and exit. Operations show that it suffers from appreciable flow fluctuations and blowouts in the tailwater, which leads to gate operation restrictions. For the purpose of understanding the hydraulic phenomenon, both prototype discharge tests and three-dimensional computational fluid dynamics (CFD) modeling of two-phase flows are performed. The operational focus of the facility are small and large gate openings. The CFD results reveal that, with air entrained in the gate shaft, continual breakup and coalescence of air bubbles in the conduit typify the flow. At small openings below 1 meter, the air–water flow is characterized by either distinct blowouts of regular frequency or continuous air release. In terms of geyser behaviors inclusive of frequency, the agreement is good between field and numerical studies. At large openings, the gate becomes fully submerged, and the flow is discharged without air entrainment and blowouts. The paper showcases the air–water flow features in a typical bottom outlet layout in Sweden, which is intended to serve as an illustration of the study procedure for other similar outlets.